Studies on reliability and failure mechanisms of dynamoelectric machines with multiturn stator coils indicate that stator insulation breakdown is one of the major causes of failure. Additionally there is evidence that the majority of stator winding failures in such machines result from turn insulation breakdown. In some cases where there has been minimal or no core damage due to the fault, it is possible to isolate the damaged coil from the rest of the winding and restart the machine. Such an operation may necessitate isolation of other coils in order to retain balanced operation of the machine. In this way the machine can be returned to service quickly, albeit with degraded performance until a more complete repair or winding replacement can be scheduled. Unfortunately location of the failed coil is difficult and time consuming.
The object of the present invention is to provide a method of, and a device for, detecting the occurrence of a shorted turn and indicating its location in the stator winding of the machine while the machine is still running.